1. Field of the Invention
This invention relates to methods and devices for generating high-pressure fluid jets, and more particularly, to methods and devices for generating fluid jets having a controlled level of coherence.
2. Description of the Related Art
Conventional fluid jets have been used to clean, cut, or otherwise treat substrates by pressurizing and focusing jets of water or other fluids up to and beyond 100,000 psi and directing the jets against the substrates. The fluid jets can have a variety of cross-sectional shapes and sizes, depending upon the particular application. For example, the jets can have a relatively small, round cross-sectional shape for cutting the substrates, and can have a larger, and/or non-round cross-sectional shape for cleaning or otherwise treating the surfaces of the substrates.
One drawback with conventional fluid jets is that they may tear or deform certain materials, such as fiberglass, cloth, and brittle plastics. A further drawback is that the effectiveness of conventional fluid jets may be particularly sensitive to the distance between the substrate and the nozzle through which the fluid jet exits. Accordingly, it may be difficult to uniformly treat substrates having a variable surface topography. It may also be difficult to use the same fluid jet apparatus to treat a variety of different substrates. Still a further disadvantage is that some conventional fluid jet nozzles, particularly for non-round fluid jets, may be difficult and/or expensive to manufacture.
Accordingly, there is a need in the art for an improved fluid jet apparatus that is relatively simple to manufacture and is capable of cutting or otherwise treating a variety of substrates without being overly sensitive to the stand-off distance between the nozzle and the substrate. The present invention fulfills these needs, and provides further related advantages.
Briefly, the present invention provides a method and apparatus for controlling the coherence of a high-pressure fluid jet. In one embodiment of the invention, the fluid jet can include two fluids: a primary fluid and a secondary fluid. The primary fluid can pass through a nozzles orifice and into a downstream conduit. At least one of the nozzle and the conduit can have an aperture configured to be coupled to a source of the secondary fluid such that the secondary fluid is entrained with the primary fluid and the two fluids exit the conduit through an exit opening.
In one aspect of this embodiment, the pressure of the primary and/or the secondary fluid can be controlled to produce a desired effect. For example, the secondary fluid can have a generally low pressure relative to the primary fluid pressure to increase the coherence of the fluid jet, or the secondary fluid can have a higher pressure to decrease the coherence of the fluid jet. In another aspect of this embodiment, the flow of the secondary fluid can be reversed, such that it is drawn in through the exit opening of the conduit and out through the aperture.
In a method in accordance with one embodiment of the invention, the fluid jet exiting the conduit can be directed toward a fibrous material to cut the material. In another embodiment of the invention, the conduit can be rotatable and the method can include rotating the conduit to direct the fluid jet toward the wall of a cylindrical opening, such as the bore of an automotive engine block.
In still further embodiments, other devices can be used to manipulate the turbulence of the fluid passing through the nozzle and therefore the coherence of the resulting fluid jet. For example, turbulence generators such as an additional nozzle orifice, a protrusion, or a conical flow passage can be positioned upstream of the orifice to increase the turbulence of the flow entering the nozzle orifice.